1. Technical Field
Embodiments of the present invention relate to a fluid ejection device.
2. Related Art
A liquid jet knife configured to excise (dissect or debulk) a soft biological tissue by continuously ejecting a liquid (water, for example) from a nozzle at a high speed is an example of a medically used fluid ejection device. An excision method using this liquid jet knife is characterized by being free from heat damage and having high tissue selectivity, and is capable of preserving microscopic blood vessels or nerves. Therefore, therapies using this system, especially in abdominal surgeries, are in widespread clinical use.
However, because the above-described liquid jet knife uses a continuous flow of liquid, the amount of liquid ejected is significant. As a result, droplets of the liquid may splash outside of an operation site may occur and the amount of liquid ejected can make surgery difficult. In fact, the ability to maintain or secure visibility is difficult due to the generation of air bubbles or the accumulation of liquid (e.g., water) in the operation site.
Accordingly, a liquid pulse jet knife configured to eject liquid intermittently instead continuously has been proposed (for example, see JP-T-2003-500098 and JP-A-2003-111766). Since the liquid pulse jet knives described in these documents eject liquid intermittently, an impact pressure is generated instantaneously at a location where the ejected liquid hits. Therefore, a liquid pulse jet knife that ejects liquid intermittently can be used to perform excisions with a small amount of flow that are equivalent to the excisions performed with liquid jet knifes employing a continuous flow. Devices disclosed in JP-T-2003-500098 and JP-A-2003-111766 are configured to eject liquid by generating a vapor bubble. In JP-T-2003-500098, the vapor bubble is generated by electric discharge from an electrode, and in JP-A-2003-111766, the vapor bubble is generated by a laser.
In conventional pulse jet knives that use vapor bubbles to eject liquid, the fluid is pushed by the vapor bubbles towards the nozzle. However, the vapor bubbles also cause the fluid to flow contrary to the fluid supply direction. Therefore, a problem arises in that the speed and the amount of the fluid ejected from the nozzle is reduced (that is, the ejection intensity is lowered).